Measuring and displaying tractor performance

ABSTRACT

A method of measuring and displaying track-type tractor performance in real time calculates both a measure of work performance and a theoretical optimum work performance for a given input state, such as track speed. After estimating soil conditions, the theoretical optimum is estimated using an iterative technique. The optimum and current performance are normalized and displayed using a first bar representing a full range of work performance, a second bar depicting a range of optimum performance for current conditions is presented overlying the first bar, and an indicator line showing the current performance. This allows an operator to adjust speed or load accordingly. A coefficient of traction and a shear modulus adjustment, reflecting soil conditions, are calculated at the tractor during operation and used to offset a table of ideal condition operating points to produce the second bar.

TECHNICAL FIELD

The present disclosure generally relates to large track-type tractorsand more specifically to measuring and displaying performance oftrack-type tractors during operation.

BACKGROUND

Owning and operating a large piece of earthmoving equipment can beexpensive. Operating cost is a function of efficient use and the impactof carrying too small or too large a load, operating in the wrong gear,etc., can dramatically increase that cost. However, the factors thatimpact efficient use are often hard to measure because soil conditions,operator selections such as gear and engine speed, and ground slope atthe worksite all effect efficiency. Further, operators are oftenprovided with an overload of information intended to improve efficiencybut which may often simply overwhelm the operator and cause them toignore potentially useful information.

For example, U.S. Pat. No. 7,557,726 presents, among a number of otheritems, a numerical indication of actual conditions and a numericalindication of the limit for that value. The operator may use a button toselect between actual load/safe working load or lift/operating radiusand then as either an absolute value or percentage. However, theoperator is tasked with determining to what extent the currentperformance deviates from the limit value as well as to decide which ofthe selectable outputs is most relevant.

SUMMARY OF THE DISCLOSURE

In a first aspect of the disclosure, a method of optimizing performancein a track-type tractor includes receiving inputs from the track-typetractor related to a current operating state, detecting a work cycle,estimating a work cycle distance from the work cycle, measuring anoperating slope, developing a track-soil model corresponding to acurrent operating environment based on the received inputs, anddetermining the current operating state using the operating slope, agear, a drawbar pull, and at least one of a groundspeed or a trackspeed. The method may include calculating a performance corresponding tothe current operating environment and the current operating state,calculating an optimum operating state and an optimum performance usingthe track-soil model, the work cycle distance, and the operating slope,normalizing the performance to the optimum performance to produce anormalized performance, and providing the normalized performance and theoptimum operating state to a device used in adjusting the currentoperating state to improve or maintain the performance of the track-typetractor.

In another aspect, a system for optimizing performance in a track-typetractor includes a ground speed sensor that provides a groundspeed, atrack speed sensor that provides a track speed, a slope sensor thatprovides a slope value, a gear sensor that provides a current gear, aprocessor coupled to each of the ground speed sensor, the track speedsensor, the slope sensor, and the gear sensor, and one or more sensorsthat provide information used by the processor to develop a drawbar pullvalue. The system may also include a memory coupled to the processorthat stores executable code that cause the processor to use the groundspeed, the track speed, the slope value, the current gear, and thedrawbar pull value to i) calculate adjustment factors for a nominalpull-slip curve, ii) develop an optimum operating state value in termsof track slip for a current operating condition based on application ofthe adjustment factors to the nominal pull-slip curve, and iii) generatea current value of performance. The system may also include a devicethat receives the optimum operating state value and the current value ofperformance for use in adjusting an operating state of the track-typetractor to improve performance.

In yet another aspect, a method of optimizing performance in atrack-type tractor includes providing a nominal pull-slip curve for anominal soil condition, receiving data from at least one sensor of thetrack-type tractor, the data including two or more of track speed,groundspeed, slope, and gear, and using the data for calculating adrawbar pull, estimating a coefficient of traction, and developing amodified pull-slip curve by applying the coefficient of traction to thenominal pull-slip curve. The method may include solving a performancemeasurement equation based at least in part on the data and the modifiedpull-slip curve to determine a peak performance metric for a currentoperating environment, developing a range of optimum operating statesassociated with the peak performance metric of the track-type tractorfor the current operating environment, and providing the range ofoptimum operating states associated with the peak performance metric anda current performance of the track-type tractor to a device for use inadjusting one or more current operating states of the track-typetractor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified view of a track-type tractor;

FIG. 2 is a diagrammatic illustration of a track-type tractor controlsystem;

FIG. 3 is a simplified and exemplary block diagram illustratingcomponents of a controller used to measure and optimize performance in atrack-type tractor;

FIG. 4 is a flow chart illustrating a method of measuring andcalculating tractor performance;

FIG. 5 illustrates an exemplary drawbar pull vs. track speed curve;

FIG. 6 illustrates a nominal pull-slip curve;

FIG. 7 illustrates an exemplary reverse speed vs. slope graph;

FIG. 8 is a flow chart illustrating determination of a coefficient oftraction (COT);

FIG. 9 illustrates a histogram of COT estimates illustrating a noisetail;

FIG. 10 illustrates a nominal pull slip curve adjusted for coefficientof traction;

FIG. 11 is a flow chart illustrating determination of a shear modulusadjustment factor;

FIG. 12 illustrates a nominal pull slip curve adjusted for coefficientof traction and shear modulus adjustment factor;

FIG. 13 is a flow chart illustrating determination of an optimumoperating state;

FIG. 14 is a graph showing a normalized performance curve;

FIG. 15 shows an exemplary pull-weight ratio vs. performance operatingrange;

FIG. 16 shows an exemplary track speed vs. performance operating range;

FIG. 17 shows an exemplary track speed vs. pull-weight operating range;

FIG. 18 illustrates target performance mapping;

FIG. 19 illustrates an exemplary mapping transfer function;

FIG. 20 is a screen shot illustrating an exemplary display of currentand optimum operating states;

FIG. 21 is a screen shot illustrating another exemplary display ofcurrent and optimum operating states with slope indicators; and

FIG. 22 shows an expanded cycle power equation.

DETAILED DESCRIPTION

Most major construction projects and many smaller projects requirereshaping the earth on or around the worksite. Earth moving equipmentcomes in many shapes and sizes including, but not limited to, graders,backhoes, earthmovers, and bulldozers. Each of these different types ofequipment is targeted to specific tasks related to earth moving. Thisdisclosure is generally directed to a category of equipment referred toas track-type tractor and more specifically large track-type tractorsusing a front blade, such as a bulldozer.

In analyzing the performance of such machines, two major elements are atplay, the operating conditions and the operating state. The operatingcondition or environment is generally described as those things outsidethe operator's control and include, but are not limited to, the slope ofthe work area, the material being moved, and the distance the materialis moved, known as the cycle distance. Operating conditions also includethe characteristics of the machine itself, such as weight and rollingresistance. Operating state generally refers to those things under theoperator's control and include gear selection, engine speed, drawbarpull, track speed, and ground speed. Drawbar pull as used here refers tothe force delivered to the tracks. This force may be expended primarilyby moving the tractor, e.g., pushing a load, and by moving materialunder the track 18 in the form of track slip. Other force may beexpended via friction losses and may be accounted for in drawbar pull.Conversely, energy diverted for other purposes such as air conditioningmay be outside drawbar pull calculations but may affect overalloperation.

When using a track-type tractor to reshape a site, the work of moving avolume of earth from one location to another may be broken into fourdistinct operations: load, carry, spread, and return. The load operationincludes lowering a blade during forward motion to scrape soil from aparticular area. The carry operation moves the removed soil to a newlocation and the spread operation allows the removed soil to unload fromthe blade, for example, by gradually lifting the blade and allowing thesoil to fall underneath a blade edge. The return operation involvesreversing the track-type tractor and driving back to a location to begina new load operation. Collectively, the four operations may be referredto as a work cycle.

While operation of such equipment is simple in concept, the cost ofowning and operating such large equipment invites, if not demands, theequipment be operated as close to its optimum performance as ispossible. For example, very light loading of the blade may allow highspeed operation but may require a significant increase in number of workcycles to accomplish the desired task. Alternatively, very heavy loadingof the blade may substantially increase the amount of track slip andslow forward progress to a point that an excessive amount of time isrequired for a particular work cycle.

Further, the slope of a worksite will affect work cycle efficiencydepending on whether the carry operation is uphill or downhill. Otherfactors may also affect selection of operating state, for example,operating at the highest possible speed in reverse may be efficient froma cycle time perspective. However, running at high speed may cause unduewear on components and negatively affect long term cost of operation andso may not be the overall best choice. For example, in some largetractors, the highest gear is prevented from use in reverse.

FIG. 1 is a simplified view of a track-type tractor 10. The tractor 10may include a cab 12, a blade 14 operated by one or more hydraulicelements 16 and a track 18, usually one of a pair of tracks, made up ofshoes (not individually depicted) that is driven by a drive wheel 20.The track 18 may engage a surface of a worksite 22, such as soil,gravel, clay, existing structures, etc. When describing operation of thetractor at an angle, a fore-aft angle θ may be measured between a planeof the track 18 and the horizontal. Similarly, a side slope of an angleφ may be measured between a line through both tracks 18 and thehorizontal. As used below, a composite of side slope and fore-aft slopeis combined and referred to simply as angle θ.

FIG. 2 illustrates a worksite 22 with an exemplary track-type tractor 10performing a predetermined task. Worksite 22 may include, for example, amine site, a landfill, a quarry, a construction site, or any other typeof worksite 22. The predetermined task may be associated with alteringthe current geography at worksite 22 and may include, for example, agrading operation, a scraping operation, a leveling operation, a bulkmaterial removal operation, or any other type of geography alteringoperation at worksite 22.

Track-type tractor 10 may embody a mobile machine that performs sometype of operation associated with an industry such as mining,construction, farming, or any other industry. For example, track-typetractor 10 may be an earth moving machine such as a dozer having a blade14 or other work implement movable by way of one or more motors orhydraulic cylinders 16. Track-type tractor 10 may also include one ormore traction devices 18, which may function to steer and/or propeltrack-type tractor 10.

As best illustrated in FIG. 2, track-type tractor 10 may include anengine 30 and a transmission 32 coupling engine 30 to traction devices18.

Engine 30 may embody an internal combustion engine such as, for example,a diesel engine, a gasoline engine, a gaseous fuel powered engine, orany other type of engine apparent to one skilled in the art. Engine 30may alternatively or additionally include a non-combustion source ofpower such as a fuel cell, a power storage device, an electric motor, orother similar mechanism. Engine 30 may be connected to transmission 32via a direct mechanical coupling, an electric or hydraulic circuit, orin any other suitable manner.

Transmission 32, in some embodiments, may include a torque converterdrivably connected to engine 30. Transmission 32 may produce a stream ofpressurized fluid directed to a motor 34 associated with at least onetraction device 18 to drive the motion thereof. Alternatively,particularly in non-track-type tractor embodiments, transmission 32could include a generator configured to produce an electrical currentused to drive an electric motor associated with any one or all oftraction devices 18, a mechanical transmission device, or any otherappropriate means known in the art.

Track-type tractor 10 may also include a control system 36 incommunication with components of track-type tractor 10 and engine 30 tomonitor and affect the operation of track-type tractor 10. Inparticular, the control system 36 may include a ground speed sensor 40,an inclinometer 42, a torque sensor 44, a pump pressure sensor 46, anengine speed sensor 48, a track speed sensor 50, a controller 52, anoperator display device 54, and an operator interface device 56.Controller 52 may be in communication with the engine 30, ground speedsensor 40, inclinometer 42, a torque sensor 44, a pump pressure sensor46, an engine speed sensor 48, a track speed sensor 50, an operatordisplay device 54, and an operator interface device 56 via respectivecommunication links. When the transmission 32 is a mechanicaltransmission, the transmission 32 may include a gear sensor (notdepicted).

Ground speed sensor 40 may be used to determine a ground speed oftrack-type tractor 10. For example, ground speed sensor 40 may embody anelectronic receiver that communicates with one or more satellites (notshown) or a local radio or laser transmitting system to determine arelative location and speed of itself. Ground speed sensor 40 mayreceive and analyze high-frequency, low power radio or laser signalsfrom multiple locations to triangulate a relative 3-D position andspeed. Ground speed sensor 40 may also, or alternatively, include aground-sensing radar system to determine the travel speed of thetrack-type tractor 10. Alternatively, ground speed sensor 40 may embodyan Inertial Reference Unit (IRU), a position sensor associated withtraction device 18, or any other known locating and speed sensing deviceoperable to receive or determine positional information associated withtrack-type tractor 10. A signal indicative of this position and speedmay be communicated from speed sensor 48 to controller 52 via itscommunication link.

Inclinometer 42 may be a grade detector associated with track-typetractor 10 and may continuously detect an inclination of track-typetractor 10. In one exemplary embodiment, inclinometer 42 may beassociated with or fixedly corrected to a frame of track-type tractor10. However, inclinometer 42 may be located on any stable surface oftrack-type tractor 10. In one exemplary embodiment, inclinometer 42 maydetect incline in any direction, including a forward-aft direction andside-to-side direction, and responsively generate and send an inclinesignal to controller 52. It should be noted that although thisdisclosure describes inclinometer 42 as the grade detector, other gradedetectors may be used. In one exemplary embodiment, the grade detectormay include two or three GPS receivers, stationed variously around thetrack-type tractor 10. By knowing the positional difference of thereceivers, the inclination of track-type tractor 10 may be calculated.Other grade detectors also may be used.

Torque sensor 44 may be operably associated with transmission 32 todirectly sense torque output and/or output speed of transmission 32. Itis contemplated that alternative techniques for determining torqueoutput may be implemented such as monitoring various parameters oftrack-type tractor 10 and responsively determining a value of outputtorque from transmission 32, or by monitoring a torque command sent totransmission 32. For example, engine speed, torque converter outputspeed, transmission output speed, and other parameters may be used, asis well known in the art, to compute output torque from transmission 32.Torque sensor 44 may send to controller 52 a signal indicative of thetorque output and/or output speed of transmission 32. Torque may be usedin calculating drawbar pull (DBP), a component of performancemeasurement as discussed in more detail below.

Pump pressure sensor 46 may be mounted to transmission 32 to sense thepump pressure. In particular, pump pressure sensor 46 may embody astrain gauge-type sensor, a piezoresistive type pressure sensor, or anyother type of pressure sensing device known in the art. Pump pressuresensor 46 may generate a signal indicative of the pump pressure and sendthis signal to controller 52 via an associated communication link.

Engine speed sensor 48 may be operably associated with the engine 30 todetect the speed of engine 30. In one exemplary embodiment, engine speedsensor 48 may measure the rotations per minute (rpm) of an output shaftor cam shaft.

The track speed sensor 50 may be used to determine the speed of thetrack 18. A second track speed sensor (not depicted) may be used todetermine the speed of the other track 18 so that a differential oftrack speed may be determined. In combination with the ground speedsensor 40, a value of track slip, also referred to simply as slip, maybe calculated, which is a function of ground speed and track speed.

Operator display device 54 may include a graphical display stationedproximate the operator in an operator station (not depicted) to reflectthe status and/or performance of track-type tractor 10 or systems orcomponents thereof to the operator. Operator display device 54 may beone of a liquid crystal display, a CRT, a PDA, a plasma display, atouchscreen, a monitor, a portable hand-held device, or any otherdisplay known in the art.

Operator interface device 56 may enable an operator of track-typetractor 10 to interact with controller 52. Operator interface device 56may comprise a keyboard, steering wheel, joystick, mouse, touch screen,voice recognition software, or any other input device known in the artto allow an operator to interact with controller 52. Interaction mayinclude operator requests for specific categorized information fromcontroller 52 to be displayed via operator display device 54.

Controller 52 may determine a current operating mode from a manualindication of an operator via operator interface device 56. For example,operator interface device 56 may contain buttons or any other method ofindicating to controller 52 the intended operating mode. It is alsocontemplated that controller 52 may automatically determine currentoperating mode by receiving input from operator interface device 56 andanalyzing the input. For example, operator interface device 56 mayinclude one or more joysticks to control both track-type tractor 10 andwork implement 14. As an operator of track-type tractor 10 manipulatesoperator interface device 56 to steer track-type tractor 10 aroundworksite 22 and to operate work implement 14 to alter the geography ofworksite 22, operator interface device 56 may send the operating signalsto controller 52. Controller 52 may then affect the operation of engine30 and related drive train components accordingly to correspond with therequested manipulation. In addition to using the signals from operatorinterface device 56 to control track-type tractor 10 and work implement14, controller 52 may further analyze the signals to automaticallydetermine a machine operating mode. For example, when an operator usesoperator interface device 56 to request a downward movement of workimplement 14 into worksite 22, controller 52 may determine thattrack-type tractor 10 is in a load mode. Alternatively, if an operatorrequests work implement 14 to remain engaged with worksite 22 whilerequesting transmission 32 to propel traction devices 18, controller 52may determine that track-type tractor 10 is in a carry mode. Byanalyzing the requested or measured location and orientation of workimplement 14, the requested or measured pressures of hydraulic cylinders16, the requested or measured speed of traction devices 18, and/or therequested or measured parameters of any component of track-type tractor10, controller 52 may automatically determine a current operating mode.Controller 52 may include appropriate hardware or software forperforming such an analysis.

FIG. 3 illustrates an exemplary controller 52. The controller 52 mayinclude a processor 70 and a computer readable memory 72 connected by abus 74. The processor 70 may be any of a number of known computerprocessor architectures, including, but not limited to, single chipprocessors or conventional computer architectures. The computer readablememory 72 may be any combination of volatile and non-volatile memory,including rotating media, flash memory, conventional RAM, ROM or othernon-volatile programmable memory, but does not include carrier waves orother propagated media. The controller 52 may also include acommunication port 76 providing support for communication with externaldevices, such as an engine computer or radio for communication with anexternal system, via a network 78.

A series of sensor inputs may be coupled to the bus 74. Each sensorinput may have a common configuration but in some cases may be tailoredto a particular sensor type and may provide specific conversion orconditioning based on the sensor to which it is coupled. For example, asensor input coupled to an analog device may provide ananalog-to-digital conversion. In an embodiment, sensor inputs mayinclude a torque or drawbar pull sensor input 80, a groundspeed sensorinput 82, a track speed sensor input 84, a slope sensor input 86, and agear sensor input 88, when needed.

Several outputs may also be provided, including but not limited to, anoutput 90 that drives an operator display device 54, an output 92 thatdrives an automatic control system (not depicted), for example, thatmanages blade load.

The memory 72 may include storage for various aspects of operation ofthe controller 52 including various modules implementing an operatingsystem 94, utilities 96, and operational programs 98, as well asshort-term and long-term storage 100 for various settings and variablesused during operation.

The operational programs 98 may include a number of modules that performfunctions described below. Such modules may include, but are not limitedto, an input module that receives data corresponding to both anoperating condition of the track-type tractor 10 and an operating stateof the track-type tractor 10, a performance module that calculates acycle power value for the track-type tractor 10, an optimizer modulethat calculates performance levels for a range of input states andidentifies an optimum performance level and an optimum operating stateof the track-type tractor 10. The modules may also include a scalingmodule that prepares a weighted target range of operation as anon-linear representation of performance values so that the weightedtarget range is a subset of performance values centered at the optimumperformance level. This may allow a narrow range of values near theoptimum performance level to be weighted more heavily than performancevalues outside the weighted target range. The modules may also include anormalization module that divides the cycle power value by the optimumperformance level to create a normalized performance level and a displaymodule that presents the normalized performance level relative to theweighted target range for use by an operator in adjusting the operatingstate of the track-type tractor 10, the target range. These functionsare discussed in more detail below.

FIG. 4 is a flow chart illustrating a method 110 of measuring andcalculating tractor performance. Overall, the goal of the system andmethod disclosed here is to estimate a current optimum performance andoptimum operating state for a track-type tractor 10, measure a currentperformance and operating state, and present an output based on acomparison of the two. In one embodiment, the output may be to anautomated system used to adjust an operating state of the track-typetractor 10. In another embodiment, the output may be directed to anoperator display so that the operator can visually see the tractor'scurrent performance compared to the optimum performance so that theoperator can adjust the operating state accordingly.

Track-Type Tractor Performance

Regarding nomenclature, the following definitions are understood to meanthe following: Operating conditions or operating environment refer tothings out of the operator's immediate control, including slope,material parameters, and cycle distance. Operating state refers tothings under the operator's control, including gear, engine speed,drawbar pull, track speed, and ground speed. Further, severalabbreviations are used below, particularly in equations, these terms aredefined as:

DBP=drawbar force

RollRes=rolling resistance

m=machine mass

g=gravitational constant

θ_(Pitch)=slope

v_(GndSpd)=ground speed

v_(Trkspd)=track speed

v_(rev)=track speed in reverse

T_(Carry)=carry duration

T_(Cycle)=cycle duration

T_(Load)=load segment duration

d_(Load)=load segment distance

T_(Spread)=spread segment duration

d_(Spread)=spread segment distance

d_(Carry)=carry distance

d_(cycle)=cycle distance (that is, the forward travel of the track-typetractor 10)

Track type tractors (TTT) are limited in the amount of torque they cangenerate by three primary factors:

1) Engine/driveline capabilities

2) Machine weight

3) Track and soil interactions

Referring to FIG. 5, a graph 140 illustrates driveline capabilities(engine 30, torque converter and/or transmission 32) as represented by adrawbar pull (DBP) curve 142. The area under the drawbar pull curve 142is track power, representing the maximum amount of power the tractor 10can deliver. The DBP curve 142 illustrates, for an exemplary track-typetractor 10, that the highest DBP, measured in kiloNewtons, is developedat low track speed. Two practical limits also apply to the DBP curve 142as the driveline cannot generate a greater propulsive force through thetracks 18 than the material can support through a resistive force. Thefirst, illustrated by the weight limit line 144, is that the amount ofpropulsive force delivered is limited by the weight of the machine. Morespecifically, the resistive force generated by the material is afunction of the normal force of the tractor 10 through the contributionof the frictional component of the soil strength. At best, soil canproduce a resistive force equal to the normal force of the tractor 10.That is, the normal force of the tractor 10 on the work surface underideal conditions limits the amount of propulsive force delivered to, forexample, the load on the blade 14. However, the work surface rarelyprovides an ideal condition with respect to soil strength.

With respect to the second practical limit, intuitively, a dry clay worksurface provides better traction than sand or snow. Therefore, thesecond, lower, limit line is known as the coefficient of traction (COT)limit 146. The COT limit is a function of the surface area of the track18 in contact with the material which contributes to the maximumtractive capacity through cohesive strength of the soil. The DBP curvefor a particular tractor may be used to estimate DBP in terms of trackspeed as found in the optimum performance solver calculations below.

The effect of soil conditions are further exemplified by the graph 150in FIG. 6 by a pull-slip curve 152. The pull-slip curve 152characterizes a ratio of drawbar pull and weight of the tractor 10 vs.track slip. Slip may be measured when ground speed and track speed areboth available, but in some cases, slip may need to be estimated usingother quantities. To summarize the graph 150, when track slip is at ornear zero, drawbar pull values are also very low, for example, whencarrying a very light load. At the other end of the curve 152, whentrack slip is at 100%, the drawbar pull is virtually equal to the shearstrength of the soil. At both ends of the curve 152, little or no workis produced either because the load is extremely light or the tracksslip so much there is no forward progress. There is a range of slipvalues near the knee of the curve 152 where peak performance isachieved.

Returning to FIG. 4, the method 110 begins at a block 112 to capture andcondition, as required, inputs used in estimating actual performance andan optimum performance, such as optimum track speed. Inputs may includedrawbar pull, track speed, slope and gear. Other inputs may includeground speed, an engine deceleration command, a service brake command,and a steering command. While useful, inputs in this latter set are notalways required. Input conditioning may involve input value conversion,such as converting analog signals to digital signals, protocolconversions, such as 4-20 ma sensor input conversion, or scaling ofinput values for easier use in subsequent calculations.

At block 114, the drawbar pull (DBP) and normal force may be determined.DBP is difficult to measure directly and is calculated from measuredquantities such as drive shaft torque, torque converter measurements, orother techniques beyond the scope of the current discussion. Normalforce is the weight of the track-type tractor 10 after accounting forthe slope of the work surface, as discussed in more detail below.

The soil model subsystem 118 includes blocks for estimating COT 120,estimating shear modulus 122 (related to soil conditions) and aperformance solver 124 that determines an optimum performance for thecurrent operating environment. Each of these are discussed in moredetail below.

A block 116 estimates cycle distance for use in developing the solutionfor optimum performance at block 124. Cycle distance, the forwardportion of the work cycle, is assumed to be the same as the reversedistance, allowing cycle distance to be estimated during reversesegments,

$\begin{matrix}{d_{cycle} = {\int_{Rev}{v_{gnd}{\mathbb{d}t}}}} & (1)\end{matrix}$

where v_(gnd) is the ground speed.

Similarly, the carry distance to cycle distance ratio can be calculatedbecause, as noted above, the d_(Load) and d_(Spread) portions of thecycle are relatively fixed in normal operation so that the carry portionof the work cycle is a fixed ratio of the cycle distance:

$\begin{matrix}{\frac{d_{carry}}{d_{cycle}} = {constant}} & (2) \\{d_{carry} = {d_{cycle}\frac{d_{carry}}{d_{cycle}}}} & (3)\end{matrix}$

Eq. 3 uses the ratio of d_(carry) to d_(cycle) as a constant, e.g., inan embodiment, 0.9, then d_(carry) can be calculated as the product ofthat d_(cycle) with the constant. The value of d_(carry) is used forcalculating performance below.

Reverse speed is determined by estimating the resistive force duringreverse:(F _(Res)=RollRes+mgsin(−θPitch))  (4)

Using this resistive force as the drawbar force required to propel themachine in reverse, the 1R (first reverse gear) and 2R (second reversegear) drawbar pull curves can then be used to estimate run-out trackspeeds. The estimated soil properties (discussed below) and thecalculated resistive force in equation (4) can be used to estimate areverse slip. The estimated reverse track speeds and slips allow anestimation of reverse ground speeds for the relative gears. In otherembodiments, more than two reverse gears may be available. The maximumground speed from the available reverse gears is used as the estimatedreverse target speed. FIG. 7 is an exemplary graph 154 of reversetractor speed in reverse gear 1 156 and reverse gear 2 158 vs. a slopeof the work surface. Note that at some slopes and for some soilproperties, the tractor 10 has a higher reverse speed in gear 1 than ingear 2.

The output of block 124 may be used to drive auto-loading functions suchas an automated blade lift system that adjusts blade depth to increaseor decrease load to achieve optimum loading. Alternatively, a targetground speed may be provided to a performance management system toachieve a target operating state.

A block 126 calculates cycle power, or current performance. Cycle poweris only one formulation of performance and others may be used. Forexample, other measures of performance may include track power, groundpower, blade power, and a volumetric production. Any combination ofsensor inputs that provide the required data for performance in any ofthese formulations may be used in the following description of measuringand displaying tractor performance. For the purpose of this disclosure,performance will be focused on cycle power and defined as:

$\begin{matrix}{{{{Cycle}\mspace{14mu}{Power}} = {\left( {{D\; B\; P} - {RollRes} - {{mg}\;\sin\;\theta_{Pitch}}} \right)v_{GndSpd}\frac{T_{Carry}}{T_{Cycle}}}}{{where},}} & (5) \\{{v_{GndSpd} = {v_{TrkSpd}\left( {1 - {{slip}/100}} \right)}}{and}} & (6) \\{\frac{T_{carry}}{T_{cycle}} = \frac{\frac{d_{carry}}{v_{gnd}}}{T_{Load} + \frac{d_{carry}}{v_{gnd}} + T_{spread} + \frac{d_{cycle}}{v_{rev}}}} & (7)\end{matrix}$

and may be stated equivalently as:

$\begin{matrix}{\frac{T_{carry}}{T_{cycle}} = \frac{1}{1 + {\frac{v_{gnd}}{v_{rev}}\frac{d_{cycle}}{d_{carry}}} + {\left( {T_{Load} + T_{spread}} \right)\frac{v_{gnd}}{d_{carry}}}}} & (8)\end{matrix}$

A block 128 develops a comparison between the current cycle power fromblock 126 and the optimum cycle power calculated at block 124.

A block 130 may also take the output of block 128 and condition it foruse in display to an operator. For example, optimum and currentperformance may be normalized and expanded over a narrow range ofinterest so that the operator is given an easy-to-understand graphicalrepresentation suitable for adjusting operating state to maintain orincrease performance.

Coefficient of Traction

The estimation of COT in block 120 of FIG. 4 is shown in more detail inFIG. 8, a flow chart of a method 160 illustrating estimation ofcoefficient of traction (COT). COT adjusts the nominal pull-slip curve152 and applies mainly to the portion of the pull-slip curve 152 aboveabout 20% slip, see, e.g., FIG. 6 and FIG. 10, discussed below. At ablock 162, data related to DBP, slope, and known values of rollingresistance and mass are collected. From these a value of pull-weightratio (PWratio), which is a fraction of delivered propulsive force overthe normal force and is calculated as:

$\begin{matrix}{{PWratio} = \frac{{D\; B\; P} - {RollRes}}{{mg}\;\cos\;\theta_{Pitch}}} & (9)\end{matrix}$

where RollRes can be estimated as a function of normal force for a givenmachine and the normal force is the product of tractor mass (m) andgravitational acceleration (g, or −9.8 m/s²) as adjusted for slope. Forlevel ground with angle θ, cos(θ)=1 and the full weight of the tractor10 is developed as normal force.

Optimum Performance Solver

When a value of PWratio is calculated, a series of screens are appliedat blocks 164-172 to determine whether to keep the value. Failure tomeet the criteria at any of these points causes the current value to bediscarded and the process is continued at block 162. At block 164, thePWratio is checked to determine whether it is in an acceptable range.For example, in an embodiment, the PWratio must be between 0.5 and 1.2.(Under some conditions, PWratios above 1.0 can be generated for a shortduration.)

At block 166, the tractor 10 must be operating in a forward gear. Atblock 168, if ground speed is known, the slip may be restricted tovalues above a knee of the nominal pull-slip curve 152. For example, inan embodiment, slip must be greater than 20%. If the ground speed is notknown, block 168 may be skipped.

False COT estimates may be caused when a PWratio calculation isartificially high or low. This can be caused when measured drivelinetorque is diverted from producing tractive force. Therefore, to preventfalse readings, at block 170 the PWratio value is discarded whensteering, brakes, or implements are engaged. Similarly, at block 172,the PWratio value is discarded if the engine deceleration pedal isactive as it will reduce generated pull.

At block 174, PWratio values that pass the screens are added to previousvalues and averaged, before performing validation tests for datapopulation and data convergence. At block 176, a data population test isperformed to check on the number of samples in the average. In anembodiment, a minimum of 200-400 samples are taken. If the number ofsamples meets the data population criteria, the routine continues atblock 178.

At block 178, a convergence test is performed where the standarddeviation of the samples is evaluated and if the standard deviation isless than a threshold, the COT value is accepted. In an embodiment, thestandard deviation value may be 0.05. Optionally, at block 180, severalCOT estimates may be averaged to account for soft spots in a cycle or anartificially high or low value due to differences in ground conditions.

Particularly when ground speed is not available, an adjustment forpopulation bias may be made at block 182. Referring briefly to FIG. 9, ahistogram of COT samples 192 shows a tail 194 due to noise and othereffects. The COT estimate 196 may be offset or increased by a multipleof the standard deviation of the PWratio values to account for the noiseand other effects. Returning to FIG. 8, following the adjustment forpopulation bias, at block 184 a final value for COT is developed andstored for later use in the performance calculation process.

FIG. 10 is a graph 200 that illustrates the effect of COT on thepull-slip curve 152 of FIG. 6. Starting with a nominal pull-slip curve152 representing typical soil conditions, increasing COT has the effectof moving up the pull-slip curve 152 having a greater impact on theportion above the knee, that is, generally along a horizontal asymptoteand in a range above about 15-40% slip, resulting in a pull-slip curve204. That is, an increase in coefficient of traction allows a higherpull-weight ratio for a given value of slip. Conversely, a decreasingcoefficient of traction lowers the pull-slip ratio for a given slip, asshown by curve 206.

In an exemplary implementation for a given operating condition andoperating state, COT values may be in a range of about 0.625 to about0.635.

Shear Modulus Factor

In applications where the ground speed is available, a shear modulusadjustment factor may be developed and used to more completely determinethe pull-slip curve 152. FIG. 11 is a flow chart of a method 210illustrating determination of a shear modulus adjustment factor‘k_(adj)’ that corresponds to block 122 of FIG. 4.

Many empirical formulations exist to characterize the pull-slip curve152 of FIG. 6. These formulations generally have the form of anexponential recovery function with the exponential rate characterized bythe soil shear deformation modulus, k. Shear modulus is acharacterization of soil deformation and ranges in value from around 60mm for well compacted clay to above 250 mm for fresh snow. One exemplaryformulation is:

$\begin{matrix}{{PWratio} = {C\; O\;{T\left( {1 - \frac{k}{{slip}*{len}} + {\frac{k}{\left( {{slip}*{len}} \right)}{\mathbb{e}}^{{- {slip}}*{{len}/k}}}} \right)}}} & (10)\end{matrix}$

where len=track length.

A nominal track soil model is defined for a nominal set of conditions tocreate a nominal pull-slip curve 152.PWratio_(nominal)=COT*f(slip)  (11)

While the track soil model is directed to track-type machines, soilmodels for wheeled machines, such as agricultural tractors, wheeltractor scrapers, compactors, etc., have a similar shape and theseapplications lend themselves to similar modeling.

The exponential rate of the nominal pull-slip curve 152 can then beadjusted to allow the nominal pull-slip curve 152 to represent variousconditions of track soil interaction by applying a shear modulusadjustment factor to the slip axis of the nominal pull-slip curve 152.

$\begin{matrix}{{PWratio}_{adj} = {C\; O\; T*{f\left( \frac{slip}{k_{adj}} \right)}}} & (12)\end{matrix}$

As in FIG. 8, a pull-weight ratio is determined for a current operatingcondition and current operating state. At block 214, the pull-weightratio from block 212 is normalized by dividing the value from block 214with the COT value from block 184 of FIG. 8 to produce an intermediatevalue r_(pw). The value of r_(pw) is a function of slip and the shearmodulus factor k_(adj) as shown in Eq. 13 below. A data fittingtechnique, such as a least squares estimation algorithm may be used todevelop the shear modulus factor.

$\begin{matrix}{r_{PW} = {f\left( {s/k_{adj}} \right)}} & (13) \\{R^{2} \equiv {\sum\left\lbrack {s - {s^{\prime}k_{adj}}} \right\rbrack^{2}}} & (14) \\{s = {{{f^{- 1}\left( r_{PW} \right)}k_{adj}} = {s^{\prime}k_{adj}}}} & (15) \\{\frac{\partial R^{2}}{\partial k} = {{{- 2}{\sum{\left\lbrack {s - {s^{\prime}k_{adj}}} \right\rbrack s^{\prime}}}} = 0}} & (16) \\{{k_{adj} = \frac{\sum{ss}^{\prime}}{\sum s^{\prime 2}}}{where}} & (17) \\{r_{PW} = \frac{{PW}_{ratio}}{C\; O\; T}} & (18) \\{s = {slip}} & (19)\end{matrix}$

f( )=nominal slip pull curve (from lookup table, see, e.g., FIG. 6)

As above in FIG. 8, a series of screens are applied to determine if ther_(pw) value is retained. If any single screening criterion is not met,the value is discarded and a new value is generated at block 214.

At block 216, if no COT value is present, for example, if only anestimated initial condition of COT is in place, the value is discarded.At block 218, as above, no steering, braking, or significant implementmovement commands may be active because potentially the power divertedto these functions could lead to an inaccurate drawbar pull value.

At block 220, ground speed must be available. If ground speed is notavailable, the estimator does not execute and the nominal initial valueof the k_(adj) estimate is used. If the ground speed signal is lost, thelast known k_(adj) is maintained until the signal returns. In anembodiment, an initial value for kadj may be used, such as 1.0.

At block 222, the track-type tractor 10 must be in a forward gear. Atblock 224, the track speed must be in a specified range. In anembodiment, the range is between 50 mm/s and 1500 mm/s. At block 226,track acceleration must be below a threshold level. In an embodiment,the track acceleration threshold may be around 50 mm/s². At block 228,slip should generally be below the knee of the pull-slip curve 152although some overlap between slip percentages used in calculating COTmay occur. In an embodiment, slip may be in a range of 0.5%-40% or insome embodiments a range of about 12% to 20%. An effect of this is tolimit values of r_(pw) to below the general range of the knee of thepull-slip curve 152.

At block 230, the value of r_(pw) should be less than 0.99. That is,pull-weight ratios above the COT may be anomalous or are at least aspecial operational case and are discarded.

At block 232, a least squares estimate on the retained values may beperformed to arrive at an estimated value of k_(adj). In an embodiment,a minimum population size of 1500 samples is used. In anotherembodiment, at block 234, a minimum of three sets of k_(adj) values areaveraged to reduce sensitivity to anomalies in the cycle or to reducethe impact of varying ground conditions. An increase in the number ofsets used for an average will cause slower adjustments to materialvariation, but provides more consistency in target speeds. A lowernumber of sets used in the average will allow the system to respondquicker to material variations.

Turning briefly to FIG. 12, a graph 240 illustrates the effect ofk_(adj) on the nominal pull-slip curve 152 of FIG. 6. Decreases ink_(adj) move the nominal pull-slip curve 152 to the left, having agreater impact on the portion of curve 152 below the knee, indicatingsoil conditions that support higher pull-weight ratios for a given valueof track slip. Conversely, increasing k_(adj) move the nominal curve tothe right, indicating soil conditions that support lower pull-weightratios for a given value of track slip.

In an exemplary implementation for a given operating environment andoperating state, values of kadj may range from about 0.1 to about 1.5.(again, these numbers depend on the nominal pull-slip curve 152).

After applying the COT and k_(adj) factors to the nominal pull-slipcurve 152, slip can be estimated as:slip_(Estimate) =f ⁻¹(r _(pw))k _(adj)  (20)

That is, slip can be estimated for a given normalized pull weight ratio,r_(pw), by using the nominal pull-slip curve 152 adjusted by k_(adj).Additionally, ground speed can be estimated for the same normalizedpull-weight ratio and a given track speed using the estimated slipvalue.

Optimum Performance Solver

In order to compare current performance to optimum performance, atheoretical optimum performance may be developed. Using the cycle powerequation (5) above:

$\begin{matrix}{{CyclePower} = {\left( {{D\; B\; P} - {RollRes} - {{mg}\;\sin\;\theta_{Pitch}}} \right)v_{GndSpd}\frac{T_{Carry}}{T_{Cycle}}}} & (5)\end{matrix}$

In order to simplify the equation, Eq. 5 is restated in terms of asingle variable, in this example, track speed.

$\begin{matrix}{{{{CyclePower} = {\left( {{D\; B\; P} - {RollRes} - {{mg}\;\sin\;\theta_{Pitch}}} \right)v_{GndSpd}\frac{1}{1 + {\frac{v_{gnd}}{v_{rev}}\frac{d_{cycle}}{d_{carry}}} + {\left( {T_{Load} + T_{spread}} \right)\frac{v_{gnd}}{d_{carry}}}}}}\mspace{79mu}{{where},}}\mspace{211mu}} & (21) \\{\mspace{79mu}{v_{gnd} = {v_{trk}\left( {1 - {{slip}/100}} \right)}}} & (22) \\{\mspace{79mu}{{slip} = {{f_{SlipPull}^{- 1}\left( r_{PW} \right)}k_{adj}}}} & (23) \\{\mspace{79mu}{r_{PW} = \frac{{D\; B\; P} - {RollRes}}{C\; O\;{T \cdot {mg}}\;\cos\;\theta_{Pitch}}}} & (24) \\{\mspace{79mu}{{D\; B\; P} = {f_{DBPcurve}^{- 1}\left( v_{trk} \right)}}} & (25)\end{matrix}$

As discussed above, T_(spread) and T_(Load) are estimated as constantsand cycle distance is estimated during the reverse segments, see, e.g.,Eq. 1. After making the additional substitutions above, the cycle powerperformance equation is completely expressed in terms of track speed andknown constants, using the previously developed value for COT. The fullequation with substitutions noted is illustrated in FIG. 22.

However, reducing the performance equation to a single variable alsorenders it unsolvable analytically. Therefore, an iterative process maybe used to determine a peak value of the performance equation. Onemethod of determining the peak value is discussed below with respect toFIG. 13. The performance equation is a theoretical operating pointsolver and applies whether or not ground speed is available. In anembodiment, slip and ground speed are always calculated as outlined ineqs. 22 and 23.

Cycle power is a useful metric for cyclic operations, such as thedisclosed track-type tractor embodiments. However, these techniques forperformance modeling are equally applicable to wheeled applications suchas agricultural tractors. As these applications tend to be non-cyclic,that is, do not have defined forward and reverse portions, cycle poweris not a particularly relevant metric for calculating performance. Innon-cyclic applications, the cycle ratio T_(carry)/T_(cycle) may be setto 1 so that the cycle power equation becomes a blade or implement powerequation of the form:ImplementPower=(DBP−RollRes−mg sin θ_(pitch))υ_(Gndspd)  (26)

These applications include a track type tractor with a ripper, atrack-type tractor using in a towing application, such as a towedscraper, agricultural tractors with towed implements such as a plow,wheel tractor scrapers, compactors, motorgraders, etc. In the case ofwheeled machines, wheel speed is substituted for track speed in theabove equation.

FIG. 13 is a flow chart of a method 250 illustrating determination of anoptimum operating state. The goal of this process is to determine thehighest possible value of cycle power and the corresponding track speedby iteratively solving a performance equation over a range of trackspeeds, within a step-size limit of track speed values. If anotherperformance measurement is used, the iterative process may be applied toa different input variable. After starting at block 252, an initialvalue for operating point is set at block 254. The initial value may bea predetermined default value or may be based on a previous value from,for example, a previous result from the same work area. For example, GPSposition information may be associated with previous track speed/cyclepower values for the same work area or a time-based recognition that atrack-type tractor 10 is likely to be operating in the same area maypoint to using a recent value.

At block 256, the performance equation (Eq. 21) as substituted withequations 19-22 above is solved for a cycle power value. At block 258, adetermination is made if a peak output value has been found. Variouscriteria may be applied to determine whether a peak has been found, butmay include covering enough of the range of input values to identify atrue peak and not just identify a local maxima, that the change in valueof subsequent outputs is near zero, the output value is above athreshold, and/or that the iteration step size is below a thresholditeration step size. Practically, the shape of a performance curve 300,304 may have a relatively flat top so that further reductions initeration may not result in a significantly high peak performance valuebut conversely, may take much longer to calculate. At block 260, if thepeak output value has been found, the ‘yes’ branch from block 260 istaken and the routine ends at block 262 and the optimum value is passedto block 128 of FIG. 4 for use as discussed above.

If the peak has not been found, the ‘no’ branch from block 260 may betaken to block 264. If, at block 264, the peak has not been found butthe value is descending from the current high value, the ‘yes’ branchfrom block 264 may be taken to block 266 where the current value ofoptimum performance, in this example, the value of track speed, is setback two iterations and at block 268, the iteration step size isreduced. The process is then repeated beginning at block 256.

If at block 264, the current value is not descending from the peak, the‘no’ branch from block 264 may be taken to block 270. At block 270, if apeak is not found, the ‘no’ branch from block 270 may be taken to block272. At block 272, the current value of the input is incremented by thestep size and the routine is continued at block 256. On the other hand,if at block 270 the peak finding routine has failed, the ‘yes’ branchmay be followed to block 274.

At block 274, the routine may begin again with the initial value set asat block 254 and the iteration step size may be reduced at block 268before the iteration process is restarted at block 256. When the processis complete, the optimum performance solver will have a solution thatrepresents the optimum available performance of the track-type tractor10 and the value of the input at which this value occurs. This value maybe passed to block 128 of FIG. 4 where a normalized value of currentperformance is calculated:

$\begin{matrix}{{NormPerf} = {\frac{{Measured}\mspace{14mu}{Performance}}{{Peak}\mspace{14mu}{Performance}} \times 100}} & (27)\end{matrix}$

As discussed above, the optimum performance may be used by auto-loadingor carrying functions at block 128 of FIG. 4. For example, if optimumperformance is expressed in terms of track speed, the track speed targetmay be passed to the auto-loading or carrying function. In otherembodiments, a target ground speed may be passed to the auto-loading orcarrying function.

Further, or instead, the normalized performance and the state at whichit occurs may be passed to block 130 and conditioned for display to anoperator. FIG. 14 illustrates an exemplary curve 280 illustratingperformance mapping. Even though the normalized performance may rangefrom 0% to 100%, the top portion of normalized performance 282 occursover a disproportionally small range 284 of input values, e.g., trackspeed. The bottom portion of normalized performance 286 is relativelyuninteresting because operation in this region is probably intentionaloperation for a purpose other than efficient work production.

The performance solver of eq. 21 and the process of FIG. 13 may be runwhenever any of the input conditions changes beyond a pre-determinedlimit and may include, but are not limited to, change of forward gear,work cycle, slope, COT, or shear modulus (when available).

When ground speed is available, current actual performance can beexplicitly calculated and used in displaying current vs. optimumperformance, as described below with respect to FIGS. 21 and 22.

FIGS. 17-19 illustrate performance estimating when ground speed is notavailable. When a ground speed sensor 40 is not available, cycle power,the numerator of the normalized performance in Eq. 26 cannot becalculated. Consequently, normalized performance may be calculatedutilizing a combination of the ratios track speed to target track speedand pull-weight ratio to target pull-weight ratio. FIGS. 17-19illustrate how normalized track speed and/or normalized DBP can beconditioned to create a display metric for an operator instead ofnormalized performance.

As discussed above, when ground speed is not known, the shear modulusadjustment factor cannot be calculated, however, both pull-weight ratioand track speed can be determined FIG. 15 is a graph showing a trackspeed vs. performance curve 300 having a target range 302 of track speedcentered around an optimum track speed target. The performance curve 300may be calculated using the performance solver equation as describedabove. However, because ground speed is not known, simply knowing anoptimum track speed for a given peak value of the performance curve 300may not be enough information to assure that the tractor is trulyoperating at its optimum performance. For example, the tracks may beturning at the correct speed but the engine may be throttled back andnot producing the expected work output. To address this, a secondmeasurement may be taken for use in validating optimum performance.

Such a measurement is illustrated in FIG. 16 showing a pull-weight ratiovs. performance curve 304 with a target range 306 of pull-weight ratiocentered around an optimum pull-weight ratio. The pull-weight ratio ofthe track-type tractor may be calculated without ground speedinformation. The known track speed to drawbar pull curve of FIG. 5 maybe normalized to pull-weight ratio to account for variables such asslope and used to generate the performance to pull-weight ratio of FIG.16. The optimum pull-weight ratio can then be calculated using the knowntrack speed to drawbar pull curve and the optimum track speed target.

FIG. 17 shows a track speed vs. pull-weight ratio curve 308, similar inshape to the drawbar pull vs. track speed curve 142 of FIG. 5. Using themeasured pull-weight ratio and the measured track speed, a currentoperating point can be found on the curve 308. The target range 302 fortrack speed and the target range 306 for pull-weight ratio overlap tocreate an optimum performance zone 310. The current performance iseasily identified with respect to the optimum performance zone 310, andmore particularly to an optimum performance point within the optimumperformance zone 310 corresponding to the peak value of curves 300 and304.

Note that either of the curves 300 and 304 may be computed by theoptimum performance solver (eq. 21) whether or not current performanceis known, that is, with or without ground speed measurements. In theexemplary embodiment, the solution is given in terms of track speed.

FIG. 18 illustrates target performance mapping for use in displayingperformance to an operator. Normalized input, e.g. track speed overtarget track speed or pull-weight ratio over target pull-weight ratio,produces a normalized performance curve 320. A target range 322 isselected around an optimum value representing peak of the respectiveperformance curve, e.g., pull-weight performance curve 304, between alow target limit and a high target limit. The limits are not necessarilysymmetric around the optimum point because of the asymmetry of theperformance curve. The curve 320 is particularly suited to pull-weightratio input mapping.

The mapping function output (vertical axis) for a given input valuerepresents the location of a current performance indicator for thatinput value, discussed more below. The mapped output zone 324 isdisplayed at an expanded scale compared to the full range of performancebecause the range of interest 322 is of the most relevance to theoperator. The amount of “zoom” provided to the target range 322 is afunction of the relative slopes of the segments of curve 320 and may beselected at design time, site set up, or during operation based oncharacteristics of the performance curve and individual preference.

FIG. 19, another exemplary mapping function curve 330 is illustrated.The mapping function curve 330 is similar to the performance curve 320of FIG. 18 except that the slopes are inverted. In this embodiment, atarget range 332 may correspond to a mapped zone 334. Because theperformance curves, e.g., performance curves 300 and 304 of FIGS. 17 and18, respectively, are asymmetric, the low target may be different thanthe high target. For example, a low target value may be the target valueminus 10% and a high target value may be the target value plus 5%. Thecurve 330 may be particularly suited for use with track speed as theinput because it is desired to indicate a large load when track speed islower than the target. Therefore, the mapping curve 330 is invertedcompared to the curve 320 of FIG. 18.

In comparison, the mapping curve 280 of FIG. 14, when groundspeed isavailable, displays a cursor at a center of a display at the 100% pointand determines a direction above or below the center based on slip beinghigher or lower than the slip at the optimum performance point.Performance display is discussed in more detail below.

Reverse Performance

During the reverse segment, it is desired to travel at the top speedcapable under the given conditions without causing damage or unnecessarylong term wear on the machine. The optimum ground speed can be indicatedto the operator in a similar manner to the optimum performance duringthe carry segment. A peak run-out reverse speed was calculated duringthe cycle portion of the peak performance solver. This speed can be usedas a reverse speed target, then calculating a reverse performance metricas:

$\begin{matrix}{{RevPerf} = \frac{Speed}{{Target}\mspace{14mu}{Speed}}} & (28)\end{matrix}$

Mapping similar to that shown in FIG. 20 is applied to the desiredoperating range.

Displaying Target Performance

FIG. 20 is a screen shot 350 illustrating an exemplary display ofcurrent and optimum operating states in a window of the operator displaydevice 54 of FIG. 2. The screen shot 350 shows, among other elements, aperformance range 352 and an optimum range 354. The optimum range 354may depict a range of optimum operating state corresponding to the rangeof interest 322 of FIG. 18, or similar depictions in FIGS. 16 and 19. Acurrent performance indicator 356 shows where the current performance iswith respect to the total performance range 352 and the optimum range354. The displayed ranges and current performance are normalized andtherefore are without units and because of the mathematical relationshipbetween input state and performance, the display may reflect eithercurrent performance vs. optimum performance or a current input value vs.an optimum input value, such as track speed. An operator may use thecurrent performance indicator 356 to determine that a change inoperating state is required. The operator may choose to change theperformance in one of several ways, including increasing or decreasingblade load, increasing or decreasing track speed, or a combination ofboth. In the illustrated embodiment, when the current performanceindicator 356 is on the left side of the optimum range 354 or off theoptimum range 354 to the left, it indicates the track-type tractor 10 iscarrying too little load. If the current performance indicator 356 is onthe right side of the optimum range 354 or off the optimum range 354 tothe right, it indicates the track-type tractor 10 is carrying too muchload. Other formats are possible, as long as the convention isunderstood.

In the normalized optimum range 354, the center of the displayrepresents peak performance. Less than the peak performance is shownwith the current performance indicator moving to the right or the leftof center. In order to determine which direction to move the currentperformance indicator 356 or cursor, refer to exemplary performancecurve 300 of FIG. 15. The performance curve 300 illustrates performanceas a function of track speed. Similar curves for slip can be developedas well as others, such as the pull-weight curve 304 of FIG. 16. Each ofthese curves exhibits a peak at the highest point of the respectivecurves 300 and 304, which after normalization appears as the centerpoint of the optimum range 354. The track speed (or other metric)associated with that peak performance can be used as the reference forpolarity when displaying the current performance indicator 356. When thetrack speed is below the reference track speed, the current performanceindicator 356 will be shown to the right of the center of the optimumrange 354, indicating too much load. Conversely, when the track speed isgreater than the reference track speed, the current performanceindicator 356 will be shown to the left of the center of the optimumrange 354, indicating not enough load.

When operating near the peak performance, because of the magnificationeffect of the optimum or target performance range on the display, slightchanges in current performance may cause the current performanceindicator 356 to jump back and forth around the optimum performancepoint and cause a distraction. This effect may be reduced by adebouncing function that adds hysteresis and/or data smoothing forsuccessive inputs. The debouncing function may be applied to all valuesor only to values near the optimum performance point.

FIG. 21 is similar to FIG. 20 and illustrates a screen shot 360 havingthe performance range 352, optimum range 354 and current performanceindicator 356. FIG. 21 also shows tractor slope both fore-and-aft 362and side-to-side 364. Additional icons collectively represented by ref.no. 366 may be shown to allow access to other functions when activatedor to indicate alarm conditions but simplicity of the screen ismaintained. As shown in FIG. 20, the display is unitless, that is,absent any numerical values, while FIG. 21 shows only numerical valuesfor slope. This greatly improves the conveyance of performanceinformation “at a glance” because the operator does not have to analyzeor process any figures or memorize pre-determined critical valuesassociated with efficient operation.

When operating in reverse, the performance and associated ranges may beshown in terms of speed. During reverse, when the current performanceindicator 356 is on the left, it may indicate a slower than ideal speedand to the right may indicate a faster than ideal speed. A faster thanideal speed may be caused by operating in a not recommended gear. Theperformance range 352 illustrated in FIG. 20 may be equally adapted toreverse speed, that is, too slow is shown to the left and too fast shownto the right of the center position.

Rubber tire/rubber track, non-cyclic applications.

INDUSTRIAL APPLICABILITY

In general, providing an operator with tools to increase the efficientoperation of a piece of equipment provides benefits of both lowered costand improved performance to schedule. The simple display of currentperformance and optimum performance can ease operator transitionsbetween different machine types as well as to reduce distractions,potentially leading to safer operation. The presentation of actualperformance vs. an optimum performance based on current conditions is animprovement over prior art systems that indicate only currentperformance without respect to environment or display only standardpre-set working ranges. This system and method uses current localoperating characteristics to develop an estimate of soil conditions,that is, a model of the current work surface. When the soil conditionsare characterized, a standard operating model can be adjusted to accountfor changes in the operating environment and can be updated virtually inreal time from worksite to worksite and from hour to hour.

Components of the soil model are used to adjust up-down and right-left anominal pull-slip curve allowing simple calculations to determine anoptimum performance in terms of a single variable, such as track speed.Once the optimum performance is determined, it can be used to normalizethe current performance and present an operator with a single bar graphof performance. The bar graph may represent the full range ofperformance, an optimum range of performance, and a current performancein a single bar-style format allowing the operator to easily view andcompare current and optimum performance. The operator can then decidewhat to do to achieve better performance, such as changing track speedby adjusting the throttle or by changing blade height to adjust load.

In the case of the reverse cycle, the same bar graph display may be usedto indicate current reverse speed vs. an optimum reverse speed tomaintain a consistent look and feel for the operator, simplifyingtraining and carrying the same easy-to-comprehend display to the fullwork cycle.

Because the performance values are normalized during processing, thedisplay of optimum performance and current performance can be carriedout consistently across machine types and operating environments.Further, the ability to display this information without using anynumerical values can reduce the training required as operators movebetween machines as well as to reduce the level of distraction in thecab during operation.

These techniques are described primarily with respect to track-typetractors, but as discussed above, the soil modeling, performanceevaluation, and normalized performance display are equally applicable towheeled machines as well as non-cyclic applications.

What is claimed is:
 1. A method of optimizing performance in atrack-type tractor, the method comprising: receiving inputs from thetrack-type tractor related to a current operating state; detecting awork cycle, wherein the work cycle is a combination of load, carry,spread, and return operations of the track-type tractor; estimating awork cycle distance from the work cycle; measuring an operating slope;developing a track-soil model corresponding to a current operatingenvironment based on the received inputs; determining the currentoperating state using the operating slope, a gear, a drawbar pull, andat least one of a groundspeed or a track speed; calculating aperformance corresponding to the current operating environment and thecurrent operating state; calculating an optimum operating state and anoptimum performance using the track-soil model, the work cycle distance,and the operating slope; normalizing the performance to the optimumperformance to produce a normalized performance; and providing thenormalized performance and the optimum operating state to a device usedin adjusting the current operating state to improve or maintain theperformance of the track-type tractor.
 2. The method of claim 1, whereindeveloping the track-soil model comprises: providing a nominal pull-slipcurve; calculating a coefficient of traction (COT) corresponding toactual current operation of the track-type tractor in high slipconditions; calculating a shear modulus adjustment factor (k_(adj))corresponding to actual current operation of the track-type tractor inlow slip conditions; applying the COT and k_(adj) to the nominalpull-slip curve for use in generating the optimum operating state. 3.The method of claim 2, wherein calculating the optimum operating stateusing the track-soil model comprises iteratively solving an equationdefining performance as cycle power in terms of the track speed to finda peak representing an optimum track speed for the current operatingenvironment, the equation expressed as:${{CyclePower} = {\left( {{D\; B\; P} - {RollRes} - {{mg}\;\sin\;\theta_{Pitch}}} \right)v_{GndSpd}\frac{T_{Carry}}{T_{Cycle}}}},$where: DBP is equal to instantaneous drawbar pull, V_(Gndspd) is equalto the track speed×(1-slip/100) with slip as a function of thetrack-soil model, and T_(carry)/T_(cycle) is a ratio of carry time tocycle time.
 4. The method of claim 1, wherein providing the normalizedperformance and the optimum operating state to the device comprises thenormalized performance and the optimum operating state to a displayshowing a window with a range of optimum operating state and anindicator superimposed on the window showing a current normalizedperformance.
 5. The method of claim 1, wherein providing the normalizedperformance and the optimum operating state to the device comprisesproviding the normalized performance and the optimum operating state toan automatic blade lift mechanism for use in adjusting a load on thetrack-type tractor.
 6. A system for optimizing performance in atrack-type tractor comprising: a ground speed sensor that provides aground speed; a track speed sensor that provides a track speed; a slopesensor that provides a slope value; a gear sensor that provides acurrent gear; a processor coupled to each of the ground speed sensor,the track speed sensor, the slope sensor, and the gear sensor; one ormore sensors that provide information used by the processor to develop adrawbar pull value; a memory coupled to the processor that storesexecutable code that cause the processor to use the ground speed, thetrack speed, the slope value, the current gear, and the drawbar pullvalue to i) calculate adjustment factors for a nominal pull-slip curve,ii) develop an optimum operating state value in terms of track speed fora current operating condition based on application of the adjustmentfactors to the nominal pull-slip curve, and iii) generate a currentvalue of performance; and a device that receives the optimum operatingstate value and the current value of performance for use in adjusting anoperating state of the track-type tractor to improve performance.
 7. Thesystem of claim 6, wherein the processor, in response to execution ofexecutable code stored in the memory, calculates an adjustment of thenominal pull-slip curve as a coefficient of traction (COT) that adjuststhe nominal pull-slip curve along a pull axis of the nominal pull-slipcurve to produce a COT-adjusted pull-slip curve.
 8. The system of claim7, wherein the processor, in response to execution of executable codestored in the memory, calculates a shear modulus adjustment factor thatadjusts the COT-adjusted pull-slip curve along a slip axis of theCOT-adjusted pull-slip curve.
 9. The system of claim 6, wherein theprocessor, in response to execution of executable code stored in thememory, iteratively finds a peak of a cycle power equation using thetrack speed and the adjusted nominal pull-slip curve.
 10. The system ofclaim 6, wherein the device displays a current operating performance anda range of optimum operating state centered at the optimum operatingstate value for use by an operator in adjusting the operating state ofthe track-type tractor.
 11. The system of claim 6, wherein the deviceadjusts a blade lift mechanism to adjust the operating state of thetrack-type tractor based on the optimum operating state value and thecurrent value of performance.
 12. A method of optimizing performance ina track-type tractor, the method comprising: providing a nominalpull-slip curve for a nominal soil condition; receiving data from atleast one sensor of the track-type tractor, the data including two ormore of track speed, groundspeed, slope, and gear; using the data:calculating a drawbar pull; estimating a coefficient of traction;developing a modified pull-slip curve by applying the coefficient oftraction to the nominal pull-slip curve; solving a performancemeasurement equation based at least in part on the data and the modifiedpull-slip curve to determine a peak performance metric for a currentoperating environment; developing a range of optimum operating statesassociated with the peak performance metric of the track-type tractorfor the current operating environment; and providing the range ofoptimum operating states associated with the peak performance metric anda current performance of the track-type tractor to a device for use inadjusting one or more current operating states of the track-typetractor.
 13. The method of claim 12, further comprising estimating ashear modulus adjustment factor, wherein developing the modifiedpull-slip curve includes applying the shear modulus adjustment factor tothe nominal pull-slip curve prior to solving the performance measurementequation.
 14. The method of claim 12, wherein solving the performancemeasurement equation comprises calculating cycle power as:${{CyclePower} = {\left( {{D\; B\; P} - {RollRes} - {{mg}\;\sin\;\theta_{Pitch}}} \right)v_{GndSpd}\frac{T_{Carry}}{T_{Cycle}}}},$where DBP is drawbar pull, RollRes is a rolling resistance of thetrack-type tractor, m is a mass of the track-type tractor, g is thegravitational constant, V_(Gndspd) is a groundspeed of the track-typetractor, T_(carry) is a first time while the track-type tractor isloaded, and T_(cycle) is a second time representing the time of a fullcycle.
 15. The method of claim 14, further comprising estimating a cycledistance defined as a distance traveled in a reverse gear asd_(cycle)∫_(rev)ν_(Gndspd)dt, where rev represents reverse motion of thetrack-type tractor.
 16. The method of claim 12, wherein solving theperformance measurement equation comprises calculating performance asone of a track power, a ground power, a blade power, a cycle power, anda volumetric production.
 17. The method of claim 12, wherein providingthe range of optimum operating states comprises providing a targetground speed to an automated blade lift mechanism.
 18. The method ofclaim 12, wherein providing the range of optimum operating statescomprises providing the range of optimum operating states to a graphicaldisplay located at an operator station.
 19. The method of claim 12,further comprising: calculating a difference between a measured slip anda slip at peak productivity; and presenting via a display device anindication of a current performance vs. an optimum performance.
 20. Themethod of claim 19, wherein presenting the indication of the currentperformance vs. the optimum performance comprises expanding a scale ofthe indication of the current performance vs. the optimum performancecentered around the optimum performance.